| 摘要 |
<p>PROBLEM TO BE SOLVED: To surely detect a dead channel even when interfering waves overlapping the leading and trailing parts of a slot by detecting the peak value of the envelope of a received signal by a peak value detecting signal and detecting the dead channel based on the detected output by this peak value detection means. SOLUTION: A first IF signal obtained by converting a received signal by a first mixer 6 is added to a second mixer 8 through a first intermediate frequency filter 7 to be converted to a second intermediate frequency signal (second IF signal). This second IF signal is outputted as a received intermediate frequency signal (received IF signal) through a second intermediate frequency filter 9 and a second intermediate frequency amplifier 10. The received IF signal outputted from the amplifier 10 is made to pass through a wave detector 11 to detect its envelope and the output of this wave detector 11 is added to a peak hold circuit 12. Then this circuit 12 outputs a voltage signal corresponding to the peak value detected by the wave detector 11 as a received level signal.</p> |
